Automatic lead mechanism for gun sighting apparatus



April 5, 1949. w. I EATHERs AUTOMATIC LEAD MECHANISM FOR GUN SIGHTING APPARATUS 3 Sheets-Sheet l Filed April l0, 1946 Wd." e r W. AUTOMATIC LEAD MECHANISM FOR April 5, 1949. I EATHERS GUN SIGHTING APPARATUS 3 Sheets-Sheet 2 Filed April 10, 1946 INVENTOR.

lmfdeaizera April 5, 194%9.

w.` I EATHERs AUTOMATIC LEAD MECHANISM FOR GUN SIGHTING APPARATUS Filed April 10, 1946 3 Sheets-Sheet 5 INVENTOR, Wzzd .Zeaziz e235.

Patented Apr. 5, 1949 NT oFFlcE AUTOMATIC LEAD MECHANISM FOR GUN SIGHTING APPARATUS Ward Leathers, Brooklyn, N. Y., assignor to International Business Machines Corporation, New York, N. Y., a corporation of New York Application April 10, 1946, Serial No. 661,014

4 Claims.

The improved computing device comprising the present invention is primarily adapted for use and has been illustrated in connection with gun sighting periscopes which are conventioal equipment on armored tanks and-which have an adjustable reticle, together with deflection and elevation mechanisms for bore sighting the periscope with the gun. The invention is, however, capable of other uses and the same may, if desired, with suitable modiiication, be employed in connection with all manner of telescopic gun sighting equipment having a reticle and designed for use on moving armored vehicles, whether the latter be land or seagoing vehicles or aircraft.

The primary function of the present computing device is to correlate the rate of turn of the gun carrier relative to a xed direction in space during aiming upon or tracking of the target as against the time of flight of the projectile and to accordingly impose automatic controls upon the movements of the reticle in order that the gun may be caused to properly lead the target in traverse by the simple process of aiming, Heretofore, leading of the target during tracking has been entirely at the discretion of the gunner who has been obliged to take into consideration such factors as range, rate of movement of the target, direction of movement thereof, and rate and direction of movement of the automotive gun carrier. The proper lead for any moving target is 4a product of all of these factors which are associated with motion of the target or of the gun carrier during tracking and a change of motion of either one of them necessitates the exercise of controls which set up a rate of turn of the gun carrier relative to a fixed direction in space.

The problem of leading the target in traverse is important in tank operation. Useful ranges `are ordinarily under 1,800 yards and seldom exceed 3,000 yards because of decreased visibility of the moving targets. Muzzle velocity varies according to the type of ammunition employed and in the present instance the reticle employed in connection with the sighting device of the periscope is designed for use alternatively with tWo types of projectiles. Irrespective of the particular ammunition employed, and for which the reticle is calibrated, the essential features of the invention are in no manner altered.

Accordingly, the principal object of the present Cil invention is to provide a simplified device which `is highly compact and suitable for use as an attachment to existing periscopes and which will automatically correlate the rate of turn of the gun carrier during aiming and tracking and the predetermined known time of flight of the projectile for any given range and,kaccordingly, to

control the movement of the sighting reticle.

against a xed scale, the nature of which is determined according to principles of ballistic progression which vary for the particular ammunition employed.

In carrying out the above mentioned object, particular emphasis is placed upon the simplicity and compactness of the device and the essential features of the invention have been compressed into space requirements which, for purposes of illustration, may be compared with the size of ones st so that it may be used where essential as an adjunct to a tank periscope which in itself in tank practice is mounted on and movable in unison with the gun directly in front of the gunner in the relatively small head space provided him vand is removable in the exigencies of tank battle.

The invention embodies an integrating mechanism having but two variables, namely, rate of turn of the gun carrier and time of night of the projectile. Means are provided whereby the latter variable, namely, time of flight, may, as a result of normal bore sighting operations in elevation, be automatically set into the computer to xedly remain therein during any one particular aiming, tracking yand sighting operation for the selected range. Means are also provided whereby during normal aiming or tracking operations the rate of turn of the gun carrier may be automatically and variably set into the computer. Mere aiming or tracking in this manner serves to automatically and instantly produce resultant increments of motion which, when correlated With the selected time of night of the projectile, are applied to the reticle to vary the position thereof when the rate of turn either accelerates or decelerates and thus the correct amount of lead on the target is at all times maintained.

It will be understood that any motion or lack of motion of the gun carrier and any corresponding motion or lack of motion of the target which does not result in actual change in the rate of turn of the latter will result in no displacement of the reticle and a constant lead will be maintained as long as this condition is maintained. This holds true even though the target and carrier are in close proximity to each other and either' or both of them are moving at a, relatively high rate of speed.

Where, as in the present instance, land vehicles are involved, the matter of leading the target in elevation does not enter into the problem and, accordingly, no automatic means under the control of an integrating device are contemplated for movingthe reticle. In the particular installation illustrated herein, however, the conventional bore sighting means for shifting the position of the reticle in elevation remains undisturbed.

In 4carrying out the invention, the same'briefly involves the use of a conventional rate of turn gyroscope which is mounted on the gun Vcarrier and which is so designed as to sense any material deviation of the carrier from a fixed direction in space. The rate of turn gyroscope operates by means of a contact movable with the gyro axis and a pair of `fixed contacts mounted on the gyro casing to sense the direction of deviation ofthe gun carrier from a xed direction and accordingly to :close one or the other of two electrical circuits associated with respective relay devices. The relay devices serve to selectively reverse the iiow of current through the armature of an electric motor and the motor in turn,` depending upon the direction of rotation of its drive shaft, serves to shift the position of the reticle associated with the periscope sighting apparatus. The motor-also serves to shift in unisonthe positions of the movable Wiper arms associated with a pair of inversely wound potentiometers.` Finally, the potentiometers in turn serve between them to control the flow of current through a solenoid coil Whose armature or core exerts an iniluence upon the axis of the gyroscope tending at all times to restore the same to its neutral position, i. e., to a position wherein the sensing contacts are separated and the relay devices are not energized. Suitable adjusting devices for the electrical instrumentalities are employed and their sensitivity is such that whenthe proper adjustments are-made only such motion ofthe gun carrier as results in an actual change in the rate of turn will cause the sensing mechanism to close one or`the other relay circuit. Thus, unless a change in the rate of turn is encountered, no shifting of the reticle will result.

It should be understood that a mere change in gun heading will'not necessarily cause precession of the rate of turn gyroscope and consequent sensing functions to take place. On the contrary, a continuous and uniform turning motion of the gun carrier in azimuth will leave the sensing instrumentalities undisturbed. What is required for closure of one or the other pair of sensing contactsis a definite speed diierential,v

either positive or negative, tending to accelerate theturning movement of the gun carrier or to decelerate the same.

From the above description, it will be seen that since the motor is mechanically coupled to the reticle of the periscope `and is adapted to shift the position of the reticlein one direction or the other, depending upon the direction of rotation of the motor shaft, and also since the extent of deviation of the reticle in either direction is a function of the rate of turn as determined by the action of the gyroscope, an automatic lead 4 is alforded and this lead remains substantially accurate and correct for any given selected range, which is to say, time of night of the projectile.

The provision of an apparatus of the character set forth above being the principal object of the invention, other objects of the invention will #be pointed out in the following description and claims and illustrated in the accompanying drawings, which disclose, by way of example, the principle of the invention and the best mode, which has been contemplated, of applying that principle.

In the drawings:

Fig. 1 is a side elevational view of the computing mechanism with a portion of the machine casing broken away to more clearly reveal theV internaly operating instrumentalities thereof. In this view, the mechanism is shown applied to a conventional periscope of the type employed on `armored tanks.

Fig. 2 is a sectional view taken substantially along the line 2-2 of Fig. 1.

Fig. 3 is a sectional view taken substantially alongthe line 3-3 of Fig. 2.

Fig. 4 is a diminutive!skeletonized view of the computing mechanism showing the most essential parts thereof.

Figs. 5 andf, taken together, constitute a schematic representation of the computing apparatus showingwthe same appliedlto the movable reticle of aperisc'ope.

Fig. 7 is a schematic electrical circuit diagram of the apparatus.

In all of the above described views, like characters of reference are employed to designate like parts throughout..

l The computing apparatus is shown in Fig. 1 as being applied to a periscope of thetype employed in connection `with armored tank turrets and which is mounted' directly on the turret for viewing the terrain from within the gunners compartment. The particular periscope illustrated is standard equipment in certain tank installations of the U. S. Armyand is generally known in ordnance circles as the M-lO periscope. This instrument isshown in dotted lines in Fig. 1 and is characterized by. theprovision of a one-power optical system whichprovides a means for observing a large eld of view `and having a reticle whichcauses the patternwto appear as if superimposed onvthe target ata distance. The periscopealso has a six-power optical system which is used for sighting on `distant targets. This system is built into the body of the periscope instead of being incorporated in a separate telescopeand is ofthe focusing type with illumination being provided'for the reticle by an electric lamp. A sighting control system is employed for adjusting the line of sight of each optical system'. The present computing apparatus is associated with the reticle of the six-power optical system only.

Referring now to Figs. 1 to 6 inclusive, the periscope is designated in its entirety at I0 and includes a generally rectilinear casing I2 having aneyepiece assembly I4 including an eyepiece lens I6' associated with the six-power optical system. Thissystem also includes a reticle assembly designated `in its entirety at I8 and having left and right reticle scales 20 and 22 respectively which are labeled in practice A and B; Thepattern represented by the two reticle scales are ballistically progressive and scale A is designed for use'when using' one type of ammunition, which may be called A-type ammunition, while scale B is designed for use when using B-type ammunition. It will be understood that either A or B ammunition is capable of use interchangeably in the same artillery which is associated with the tank turret. The reticle assembly also includes a movable cross hair, indicator or reticle proper 21.

The reticle assembly I8 includes a slide member or block 24 (Figs. 1 and 4) which is adjustable vertically on a second slide member or block 26, suitable guideways 28 being provided for the purpose. The second block 26 is similarly adjustable horizontally on guideways 3l] integrally formed with the body or casing of the periscope.

The A and B scales are marked upon a transparent optical element 23 mounted in brackets 25 which are secured by means of screws 29 to Y the block 26. A cross hair 3| is also marked upon the optical element between the two scales. These scales thus are shiftable laterally in the eyepiece of the telescope but the eiect of such shifting is without signiflance inasmuch as the block 26 does not move vertically. The reticle 21 is movable with the block 24 and, toward this end, it is carried upon a circular optical piece 33 suitably mounted in the block 24. Thus for bore sighting purposes the reticle may be moved both vertically and horizontally While, according to the present invention, for purposes of leading the target, it may be automatically shifted laterally in traverse by mechanism later to be described. Means are provided for adjusting the position of the slide block 24 in a vertical direction for bore sighting in elevation and additional means are provided for adjusting the position of the block 2G laterally for bore sighting in traverse, these means being normally incorporated in the periscope assembly as originally constructed.

The actuating instrumentalities comprising the present computing device are assembled and mounted within a casing 32 (Figs. 1, 2 and 3) which is removably attached to the casing l2 of the periscope and to accommodate which certain modifications of the periscope bore sighting adjustments have been resorted to. According to the present invention, the original adjusting knob and stem therefor have been removed and in their stead an elongated stem 36, which is provided with a knob 34 passes completely through the casing 32 and extends into the casing I2 of the periscope to accommodate bore sighting operations in the usual manner. In a similar manner, the original adjusting knob and stem designed for use in bore sighting in elevation have been removed and a specially designed knob 38 and stem 40 associated with the casing 32 has been substituted therefor.

The slide block 26, which is movable laterally on the guides 30, is adjustable by virtue of a threaded socket portion 42 which receives therein an enlarged threaded portion 44 of the adjusting knob stem 36. The stem 35 (Figs. 1 and 5) is mounted for axial or longitudinal sliding movement in the casing 32, it being supported adjacent the outer side of the casing 32, in a sleeve member or guide 45. The stem 33 makes a connection, as will be described subsequently, with the upper end of an integrating arm 48. From the above description it will be seen that rotation of the stem 36, which may be effected by manipulating the adjusting knob 34, will serve to cause lateral shifting movement of the slide block 26 and consequently of the reticle 21,'aswel1 as of the scales 20 and 22, in one direction or the other by virtue of the threaded connection between the threads 44 in the socket 42. Such an adjustment is employed only duringV initial bore sighting operations in traverse and once the adjustment-has been made the angular position of the adjusting knob 34 and stem 36 is not altered. This bore sighting adjustment sets-a constant factor into the computing mechanism which remains undisturbed for any particular sighting or tracking operation. Such an adjustment is entirely a manual one which is performed at the discretion of the gunner. In addition to the bore sighting adjustment, the stem 36 may be shifted laterally under the influence of the integrating arm 48, this latter type of shifting movement being an automatic one and constituting a function of the rate of turn of the gun carrier, all as will become clear presently.

The means for adjusting the position of the slide blockV 24 vertically to raise or lower the reticle indicator 21`includes a bell crank lever 52 (Figs. 4 and 6) having an arm 54 projecting into a slot 53 vformed in the slide block 24 and having an additional arm 58 projecting into a slot 60 provided in a block 62 (see Figs. 1, 4 and 6). The block 62 is interiorly threaded as at 64 and receives therein the threaded end 66 of a shaft 68. Theshaft 68 is provided with a tubular bore 1U therein which is reduced and threaded as at 12 and threadedly receives therein the threaded end 14 of the adjusting stem which carries the elevation adjusting knob 38. The shaft 68 is splined as at 16 to a short shaft 18 associated with a-gear train mechanism subsequently to be described. It will be seen that as in the case of the bore sighting adjustment in traverse so in the present instance for 40 bore sighting in elevation an initial adjustment is made by manipulation of the adjusting knob 38. Upon such manipulation of the knob the threaded portion 14 of the stem 4D will cause shifting movement'of the shaft 68 axially to in turn cause rocking movement of the bell crank lever 52 in one direction or the otherand consequent raising or lowering of the slide block 24 together with the reticle pattern.

It should be borne in mind during the subsequent discussion that the terms rangef elevation and time of ilight of the projectile are synonymous and each refers to a single integrating factor adapted to be entered into the integrating mechanism of the computer. It is obvious that where a at terrain is concerned a distant target will require a greater elevation than will a nearby target and in this limited sense range and elevation are synonymous. It is also obvious that the greater therange the longer will the projectile have to travel in its ballistic path before reaching the target and thus in this sense the term range and time of flight of the projectile are synonymous.

Since the present computing apparatus provides an automatic lead in travsersev at any selected range and since to accomplish this it is designed to integrate the rate of turn of the gun carrier relative to a xed direction in space against the range or time of ight of the projectile, means are provided for setting into the integrating mechanism an elevation factor, which factor is indicated in the reticle assembly by a predetermined setting of the position of the reticle 2'l relative to either the vA `or B scalezg or 22. The meansjust referred; to `includes ia manual adjusting knob 80 (Figs. 2, Sand 6) mounted at the front of thecasing 32 and carried on astem or shaft 82 (see also Figsfl and 6).

The shaft 82 carries at its inner end one element of a clutch assembly 83, thev other element of the assembly being associated with a gear 84 which mesheswith a pinion 86mounted on a shaft 88. The clutch 83 has no operative function in connection with the computing mechanismfand is provided merely for/ease of assembly and disassembly of the mechanism. The shaft 68 carries a bevel gear `80 meshing With a similar gear 92 integrally formed with the hollow shaft '|8,` `which in turn is splined t0 the shaft. It ,i

vwill be seen, therefore, that upon rotation of the adjusting knob 80 motion will be transmitted through the train of gears and mechanism just described to the shaft 68 and thelatter, by virtue of its threaded engagement with the block 62, will in turn transmit elevational motion tothe slide block 24 and consequently to the reticle `27|.

Thedilerentiating mechanism of the computingV device is best illustrated in the schematic showing of Figs. 1 and 6, although'the principles involved also appear in all of the remaining figures. The stem 36 which carries the adjusting knob 34, and by means of which deection bore slghtingfoperations may be accomplished, has mounted thereon a pair of thrust collars `between which there is loosely disposed a sleeve |02 having formed therein a pair of trunnions |04 which project into openings |06 formed in a pair of'bifurcated arms |08 carried at one-end of an integrating bar 48. the bar 48 is also bifurcated as at |I2 and the bifurcations thereof straddle a guide pin H4 mounted i on an insulating block H6 through which passes a threaded rod ||8 in threaded engagement therewith.l Theinsulating block I6 carries thereon a pair of movable contact brushes |a and |201) (see also Fig. 7), each being designed for engagement with a potentiometer, which potentiometers are designated atrPl and l=.2and` the nature of which will beset forth presently. The rod ||8 is` rotatably mounted in Vbearings |22 secured to a stationary portion of the casing 32. A gear |24 mounted on the threaded rod H8 meshes with4 asimilar gear |26 carried by a` shaft |28 mounted in bearings |30. The shaft |28 is operatively connected through a pair of spiral gears |32` to a shaft |34 which carries a gear |36 that meshes with a worm |38 associated with the` shaft |40 of an electric motor M.

The integrating bar 48 is slotted centrally as at |42 and a pivot pin |44 projects completely through the slot |42. The pivot pin |44 is mounted upon a vertically movable slide `block |46 carried in guideways |48. The block |46 is adapted to be moved vertically in the guideways provided for it and to carry with it the `pivotpin |44 for the purpose of shifting vertically the fulcrum axis of the integrating bar 48 to `change the relationship between the extent of shifting movement of the stem 36 and the extent of movement of the block |6`-along thethreaded rod` l I8. Thus when the pivot pin |44 is in a position wherein it is near the bottom of the slot |42,` a comparatively small axial movement of the block H6 along the rod ||8 will result in a comparatively large axial movement of the stem 36. Conversely, when the pivot pin `|44Ais near the upper end of the slot |42 it will require a comparatively large displacement ofthe. block I|6 The opposite end` of r the reticle 21.

tofxaiorda 'comparatively `small ydisplacement of the 1 stem i 36.`

Thezposition `of the pivot pin |44fis a direct factor of therangeor; mother words, of the time of flight of theprojectilewhich is one of the input factors to be put into the computer and in-f tegrated with the factor of rate of turn. Since the time of ight ofthe projectile is naturally affunction ofthe range, either of these 4terms may bewused interchangeably in connection with the computingmechanism. The positioning of the pivotpin |44 may, therefore, be considered as one input of thecomputer and, accordingly, such positioning of the pin operates under the control of a` range cam .designated at |50. The cam |50 is pinned as at |52 to the stem or shaft 82 on which theadjusting knob is carried. The cam |50 cooperates with a cam follower arm |54 which is pivoted as at |56 to the casing 32 and spring pressed as at |58. The range cam |50 is designed according to principles of ballistic progression in such a manner that `as the range increases the camfollower is swung downwardly to cause the pivotpin |44 `tomove downwardly in the slot |42 and ,alter the fulcrum point for the integrating barll. At extremely long ranges in the neighborhood of `from 2,500 to 3,000 yards, `the pivot pini|441will occupy a` position in proximity to the lower end of the slot |42 so that very small increments of motion of the block H5 will result in'largeincrements of motion of the stem 36 and consequent large increments of displacement of the reticle 21. Conversely, at very close ranges down to point-blank range, the pivot pin `|44 will occupy a positionv adjacent the top of the slot |42, thus throwing the fulcrum point for vthe integrating bar 48 upwardly whereby large increments of motion of the block ||6 will cause relatively small incrementslof displacement of In any instance, however, by means of certain electrical instrumentalities about to be described, the reticleZl will be displaced the commensurate distance during tracking operations `for properlleading of the target for any selected range. It will be understood that dur-ing tracking `operations Vas the target moves toward orawayfrom the-gun carrier,` either by virtue' of its own motion :or byvirtue of motion ofthe gun carrier or by a combination `of both of these motions, thegunner may, by manipulationA of the knob 80, alter the range to thus change the extent of the automatic variable lead on the targetthis variable lead, of course, being a function of the rate of turn of the gun carrier.

Referring lnow to Fig. '7, the electric motor M isshown ras being provided with a eld winding Mf and with an armature Ma. Means in the form of a relay mechanism including a pair of solenoid magnets SU and SL serve to operate respective `pairs ofcontact groups CI and C2 to selectivelypass current through the windings of the armature Mw in opposite directions tovary the direction of rotation of the motor. The contact group CI includes cooperating pairs of `contacts Cla and Cib, while the contact group C2 includes cooperating pairs of contacts C2a and CED. A variable rheostat R serves to adjust the flow of current through the armature windings and thus constitutes a speed response rheostat. The" previously mentioned potentiometers PI and P2 `are inversely wound in a bridge circuit in such `a manner that as the'contact brushes |20a and'v |205 move in unison the two potentiometers are :caused between `them to control the flow of r current through an erecting coil Se `which exerts actriz-11sv an influence upon the rotor r associated with the conventional rate of turn gyroscope, the function of which is to actuate a plurality of precess contacts Cgu, Cyl and Cgc. In the normal position of the contacts Cgu, Cgl and Cgc the center contact Cgc remains out of engagement with either the upper contact Cgu or the lower contact Cgl as long as the rate of turn gyroscope casing, which is xed to the gun carrier, does not change its rate of angular motion with respect to the gyroscopic axis. When, however, the rate of turn increases or decreases in one direction or the other` the contact Cgc by its normal precessional action is caused to engage one or the other of the contacts Cgl or Cgu, thus energizing either of the solenoids SU or SL so that current will flow through the winding of the armature Ma in the proper direction, whereupon the shaft |40 of the motor M will rotate in one direction or the other and thereby perform the dual function of shifting the position of the potentiometer brushes |2|3a and |20b and automatically adjusting the position of the reticle 21.

In the operation of the computer mechanism the gunner makes his preliminary necessary bore sighting operations both for traverse and for elevation in order to align the reticle 21 with his artillery, and once these bore sighting operations have been completed for any particular maneuver no further bore sighting adjustments are resorted to. As previously described, the bore sighting operation for traverse is eifected by means of the adjusting knob 3d, while the bore sighting operation for elevation is eilected by means of the adjusting knob 38.

The next step in any particular maneuver is a determination or estimation of the range and selection of either type A or type B ammunition,

'as previously described. Depending upon the particular type of ammunition employed and upon the estimated range as furnished by the oiicer in charge of operations, the gunner will then manipulate the manual adjusting knob 80 which is the only manual control available to him for subsequent maneuvering operations. If, for example, type A ammunition is to be employed and the range has been adjudged to be 2,000 yards, the adjusting knob 80 will be turned in one direction or the other until the reticle indicator 2'! comes into register with the indicia representing 2,000 yards on the A scale 20 of the reticle assembly. It will be understood that the exact lateral positioning of the scale carrying element is immaterial since this scale is bodily movable with the block 26 and since this latter block is capable of no elevational movements. The target may then be sighted and a trial shot or volley of shots effected as a check upon the range. An observation of this shot or shots may or may not, as the case mayv be, lead to a correction of the range. If the range has been found to be satisfactory, then combat maneuvers may proceed. If not, a different range adjudged from observation of the trial shot or volley of shots will be set into the computing mechanism.

Once the range has been determined and set into the computer no further adjustments of the knob are necessary and the proper lead upon the target will be accurately maintained by the gunnerduring normal sighting or aiming operations, during which the reticle indicator 21 is maintained upon the target.

Upon initial adjustment of the knob 8|! not only is the reticle 2l brought into alignment with the selected range scale reading but also the range cam |50 is brought to a predetermined position, whereupon the position of the cam follower arm |54 is predetermined in order to set the fulcrum point |44 of the integrating bar ||0 and set into the computer the range factor which is the equivalent of the time of flight of the projectile. Unless the range changes during the particular maneuver under consideration, this factor remains a constant in the computing mechanism. The variable input factor for the computer mechanism consists in the rate of turn of the gun carrier, as will now be explained.

During normal tracking operations with the reticle 27 (Fig. 6) accurately following the target, any motion of either the target or the gun carrier, i. e., the turret, or any resultant combination of velocities of the moving elements which will cause a change in the rate of turn of the gun carrier relative to a iixed direction in space, as exemplied by the gyroscope rotor r, will cause the contact Cgc to precess either upwardly or downwardly and thus seek and engage either the upper contact Cgu or the lower contact Cgl,` as the case may be. Either a static condition of the gun carrier or a uniform rate of turning movement thereof which involves neither an increase nor a decrease in rate will not serve to disturb the center position of the contact Cyc inasmuch as the bridge circuit, including the potentiometers Pl and P2, operates to supply current to the erecting coil Se in precisely the amount required to offset the precessional tendency of the rotor r. However, when a change in the rate of turn is encountered and the con,- tact Cgc engages one or the other of its counterpart contacts, current will be caused to ilow from the source S through one or the other of the solenoids SU or SL, thereby selectively actuating one or the other of the contact groups C| or C2 in'such a manner as to pass current through the armature winding Ma and energize the motor in such a direction that the potentiometer brushes |2011 and |2l3lz` seek a position wherein just suflicient current is supplied to the erecting coil Se to again open the precess contacts. Also, during rotationof the motor, the block H6 moves along the threaded rod I I3 to tilt or swing the integrating bar 4B about its fulcrum point |44 and slide the stem 3B in one direction or the other to thus shift the position of the block 26 and consequently of the reticle 21 to indicate the proper lead for the selected range.

If, for example, because of an increase in the rate of turn of the gun carriage, the rotor 'r precesses in such a manner ,as to cause engagement between the contacts Cg,c and Cgu current will flow from the positive side of the source S through wires a, b, exible lead fl, contacts Cgc, Cgu, wire c, solenoid SU, wires d, e, and f to the negative side ofthe source. Upon energization of the solenoid SU, the normally closed contacts Cla become open and normally open contacts Clb become closed, thus establishing a circuit` from the positive side of the source through wires g, h, normally closed contacts C2a, wire f, speed responsive rheostat r, wire lc, armature Ma, wire Z, contacts Clb (now closed), and wires m and f to the source. Current flowing in this di- 11 ing'of` the erecting coil Se. In theinstance just described, current will flow in this localcircuit from the brush |2017 to the brush |2011 throughr flexible lead fl, wire n, a calibrating resistance Pc, wire o, iie'xible lead fl, erecting coilSe, flexible leadfl, wire p, flexible lead fl, to the brush la. When the bridge circuit is balanced the brushes |2lla and |2011 are at the same potential and thus no current flows through the erecting coil Se, although current does ow from the source S through wires a, q, and divides itself `through the two potentiometers` rejoining again land passing through wires s, e, and j to the source.

`The flow of current through the local erecting coil circuit just described gradually increasesas the'brushes l20a and i201) move along the rod H8v and yat the precise moment when the flow ofcurrent in the coil'Se is suiiiciently strong as f tofcounteract precessional tendency of the rotor rthe contact Cgc will leave the contact Couy to break the circuit through the coil SU and open the contacts Clb, thus stopping the motor M.

'The motor `will remain deenergized until such time as the rate of turn of the gun carrier again .encounters a change.

' Similarcircuits may be traced for aninstance wherein the Vchange in the rateo turn decreases instead of increases. In such an instance, the rtendency forfthe rotor will be to precess downwardly, thus closing the contacts CgcA and Cyl instead of the contacts Cgc and C'gu.

Itwill be understood that during any particular maneuver if the range increase or decrease, as forexample, when the target and gun carrier approach each other or move away from each.

other, the gunner may, by manipulation of the adjustinglmob` 8l) change the range or time of be limited only aslindicated by the scope of the following claims.

What is claimed is:

1. The combination with a gun sightingperiscope having a laterally movable reticle of a computing mechanism for automatically shifting said reticle laterally to effect a lead in traverse upon atarget during tracking operations, said computing mechanism comprising a rotary range cam, a cam follower cooperating with said cam, an integrating lever mounted for swinging movement about a fulcrum, means under the control of said cam follower for shifting the fulcrum of said integrating lever, means connecting one end of said integrating lever to said reticle for shifting the position of the latter, means for adjusting the position of said rotary cam according to an estimated range, and means operable upon a change in the rate of the movement of the periscope in traverse during track- "ingoperations for moving the other end of said integrating lever a commensurate amount.

2. The combination with a gun sighting peri- Ascope having a laterally movable reticle of a computing mechanism for automatically shifting said `reticle laterally to effect a lead in travshifting the position of the latter, means for adjusting the position of said range cam according to anestablished range, a threaded shaft mounted for rotation about'an axis,y a block connected to the other end of said integrating lever and threadedly received upon said shaft, a reversible electric motor, means operativelyy connecting said motor and shaft for selectively rotating the latter in opposite directions, and means operable upon a change in the rate of the movement of the periscope in traverse for selec- 'tively energizing said motor to cause the same to rotate said shaft in one direction or the other according to the direction of said change in rate and to an extent commensurate with the magnitudeof said change in rate.

3. The combination with a gun sighting periscope` having a reticle and means for moving said reticle vertically for bore sighting operations in elevation and additional means for moving said reticle horizontally for bore sighting operations in traverse, and a ballisticallycalibrated range scale associated with said reticle of a computing mechanism for automatically shifting said reticle laterally to effectsJ lead upon a target, said computing mechanism comprising a rotary range cam, a cam follower cooperating with said cam, an integrating lever mounted for swinging movement about a fulcrum and having one end thereof connected to said reticle and operable upon swinging movement to shift the 40 position of said reticle, means for adjusting the position of said range cam according to an established range, a selectively energizable reversible electric motor having a shaft, means operable upon rotation of said shaft in one 'direction for moving the other end of said lever in a corresponding direction and operable upon rotation of the shaft in the other direction to move said latter end of said lever in an opposite direction, means under the control of said cam follower for shifting the fulcrum of said integrating lever, a gyroscopic member mounted for rotation in unison with the periscope, and means operable upon a change in the rate of turn of 'the axis of said gyroscopic member for selectively energizing said motor.

4. The combination with a gun sighting peris'cope having a laterally movable reticle of a computing mechanism for automatically shifting said reticle laterally to effect a lead in traverse upon a target during tracking operations, Said computing mechanism comprising a rotary range cam,V a cam follower cooperating with said cam, an integrating lever mounted for swinging movement about a fulcrum, means under the control of said cam follower for shifting the fulcrum of said integrating lever, means for adjusting the position of said range cam according to an established range, a selectively energizable reversible electric motor, means operable upon selective energization of said motor for moving one end of said lever in opposite directions, selectively energizable relay mechanisms for energizing said motor to cause rotation thereof in either direction, a rate of turn gyroscope having a rotor and two pairsvofnormally open precess contacts associated therewith and forming a part of said relay mechanism, said gyroscope being operable upon precession thereof in either direction to close one or the other of said precessed contacts, an erecting coil for said gyroscope, a bridge circuit including a local circuit for said erecting coil, means operable upon selective energization of said motor for progressively unbalancing said 4bridge circuit to cause said local circuit to become progressively energized to counteract precession of the rotor and cause opening of said precess contacts, and means connecting the other end Number of said integrating lever to said reticle for shifting the position of the latter.

WARD LEATHERS.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date 1,936,442 Willard Nov. 21, 1923 

